48 



CARBONIFEROUS ENTOMOSTRACA. 



BelationsJiij} of the Genus. — The carapace of Entomoconchus differs from that of any 

 of the known species of Cypridina, Pldlomedes, Asterope, or Bradycinetus, in its sub- 

 quadrilateral outline, the hood and notch being only slightly developed, and usually 

 much higher up than in the oval Cypridinada. Its greater globosity and the thickness 

 of its valves distinguish it from the majority of the Cypridinal species, though the overlap 

 of the larger (left) valve is the same as in Cypridina ? Zelandica, Baird (' Proc. Zool. 

 Soc.,' Annulosa, pi. 17, figs. 11 — 13), and C. ? albomaculata, Baird (ibid., pi. 71, 

 figs. 1 a — d). The Muscle-spot of the latter has a somewhat similar character to that 

 of Entomoconchus. 



There is a superficial likeness between some of the smaller specimens of Entomo- 

 conchus and the carapace oi Limnefis Gouldii, Baird ('Proceed. Zool. Soc.,' 1862, p. 149, 

 Annulosa, pi. 15, fig. 7) ; but the Cypridinal notch is absent in the latter, and the Muscle- 

 spot is very different. 



Pigs. 1 and 7 of our Plate I have outlines somewhat similar to that of Bolycope orhicu- 

 /fl'm, Brady (' Lin. Soc. Trans.,' vol. xxvi, pi. 35, fig. 53) ; but with this the resemblance 

 ends, for in Polycope the Cypridinal notch is quite obsolete. 



With the similarly globose, but strongly hinged, Heterodesmus} an imperfectly known 

 Cypridinad from the Sea of Japan, Entomoconchus has shape and gibbosity in common, 

 but the hingements differ, as well as the form and amount of notch or sinus. 



Judging by the carapace-valves, all of the animal that remains to us, Entomoconchus 

 was a marine gregarious Bivalved Entomostracan (as indicated by M'Coy in 1839), 

 closely allied to the existing Cypridinadce ; but the high position and the feeble development 

 of its " notch " and " hood," and the vertical, narrow, interrupted anterior " gape " of the 

 valves, are distinctive features, connected with the extrusion of the antennae (swimming 

 limbs) and other organs, which were doubtlessly planned somewhat differently to those of 

 the existing genera. 



For the better understanding of the illustrations referred to we note that — 



In Prof. M'Coy's figures (1839)— 



Fig. a is the anterior aspect of a carapace, the dorsal border being to the right 

 hand of the reader, and the right valve upwards. Compare our PI. I, fig. 

 2 d, &c. 



Fig. 6 is the ventral aspect, with the anterior end upward. Compare our fig. 6 c, 

 &c. 



Fig. c is the side view of a carapace, showing the right valve and its muscle-spot ; 



the anterior end is upwards, and the dorsal border to the left of the reader. 



Compare our fig. 4 a, &c. 

 Fig. d (natural size) is an outline view of the last-mentioned aspect (or of a left 



1 G. S. Brady, 'Trans. Zool. Soc.,' 1866, vol. v, p. 387, pi. 72, figs. a—h. 



